LG 60PB6650 plasma flashes gray, then nothing

[uncaged]

Hi everyone,

My LG 60PB6650 is 3 months out of warranty and it went on the fritz! Doesn't that figure!? Hopefully, you guys can help get it straightened out.

So the TV when plugged in, immediately powers up, the whole screen flashes a solid gray for 1 second, and then goes black. Doesn't respond to anything.

Here's where I am so far:
Found some semi-similar block diagrams on toms service manuals site. They are close, but probably different enough to get me in trouble.

The power supply goes "on" and relays click as soon as AC power is applied. VS, M5A, and VA are all a couple tenths of a volt to what is printed on the board.

If I hold the power button down for 10(?) seconds, it will go into standby mode and the red LED on the front goes on (usually on when set is off, and off when the set is on). Press the power button and it powers up, the screen flashes gray, then black.

When on, the control logic board has a green blinky light.

The other diagrams I found describe checks where you unplug the "main" board from the PS board, and the MB to CB ribbon cable, then short AUTO GEN test pads on the CB to make the screen display a test pattern. That test pattern didn't appear, but then again, I don't have the right manual so I don't know if that procedure applies to this model.

It did, however, act like a possible bad MB test where the PS is supposed to go high when the MB is unplugged from it, but again, I dunno.

So, any input is much appreciated. A proper manual would be great.

Best Regards,
Mike

[Nick's Tvs]

Re: LG 60PB6650 plasma flashes gray, then nothing

Do you get sound out of the set or nothing?
have you checked the back of the Power supply for cracked solder joints?
Have you tried isolating the power supply and checked voltages?

[Alastair E]

Re: LG 60PB6650 plasma flashes gray, then nothing

Unplug Buffer-Board from Y-Main, and re-try. (Dont let screen tabs short to metalwork when testing, or there'll be a Bloody BIG bang and thats the end of it)

Does set stay on?

[uncaged]

Re: LG 60PB6650 plasma flashes gray, then nothing

Thanks for the replies.

The set was configured for digital audio out (and to disable the native speakers) when it went down. I tried giving it audio in, and nothing came out of the speakers, but haven't tried hooking up the digital audio out to the stereo amp.

The back of the power supply board doesn't appear to have any obvious cracks or cold solder joints.

I went through the voltages on the P813 connector when it is in run mode as soon as it's plugged in and (what I think is) standby mode after doing a power button hold / reset. Without the right manual, I'm trying to cross reference using manuals for a 50PJ350, 50PG20, and 60PS60, which are kinda sorta close, but all are different with some keeping 5V in STBY and some not, and labels being different for functions that I'd suspect are the same. In any event, this one is keeping 5.2V in RUN and STBY, keeping AC_ON at 5.07V in RUN and STBY, and everything else drops out on STBY. Other voltages in RUN seem plausible comparing the other manuals, but they don't all agree exactly on the values.

Alastair,

Do you mean disconnect the Y-DRIVE UPPER and Y-DRIVE LOWER (8 ribbons) from the PDP, or the CONTROL ribbon from the Y-SUS, or another one?

Thanks!

[crt man]

Re: LG 60PB6650 plasma flashes gray, then nothing

Alastair,

Do you mean disconnect the Y-DRIVE UPPER and Y-DRIVE LOWER (8 ribbons) from the PDP,

Thanks!

Yes the boards that the ribbons go in to, from the board it is connected to.

Alan

[uncaged]

Re: LG 60PB6650 plasma flashes gray, then nothing

Attached is a picture of the Y area boards so that I'm clear as to what we're talking about, because I'm still a little unsure.

The upper and lower buffer boards are attached to the Y-SUS by rigid header pin connectors. To disconnect the buffers from the Y-SUS, the Y-SUS board will have to be un-screwed and then pulled apart from the buffer boards.

Also, I tried to disconnect the orange PDP ribbons from the buffer boards, but can't figure out how they come out. There is a black flip up lever on the opposite side of the white housing from where the ribbon goes in. The white housing seems fixed to the board. The ribbon is locked in there somehow, and you can't get a good grip on it. Is there a special tool or trick to pulling the ribbon out?

Thanks for the help.

UPDATE:
I just found a blown surface mount cap, C873 on the upper Y buffer board. It goes between the ground screw pad and the big pad next to the ribbon connector that connects the upper and lower boards. So, now, why did it blow? Fault of the Y-SUS board? Do I just replace all 3 Y boards at once?

[uncaged]

Re: LG 60PB6650 plasma flashes gray, then nothing

So anyway, I've replaced the Y-SUS board and the upper Y buffer board. There's a picture now!

The screen has 2 thin horizontal lines running across it about 3 inches down from the top. What could cause that?

[hmendez86]

Re: LG 60PB6650 plasma flashes gray, then nothing

the buffer boards with the integrated ic chip are short or burn..some ic burns you can see at the look or some you cant...but if you saying are horizontal lines 3 inch just replace the buffer the upper or lower buffer, they are divided in to two parts connected with a small ribbon and attached to the Y-sustain board. depending were the line is on the top or bottom replace that buffer( if it is in the very middle of the two buffer change both)

[hmendez86]

Re: LG 60PB6650 plasma flashes gray, then nothing

if lines are flat bed=buffers boards
if line are straight up and down= are the cof bonding ic tabs(solution none)(are no reparable)

[notsogentle]

Re: LG 60PB6650 plasma flashes gray, then nothing

Attached is a picture of the Y area boards so that I'm clear as to what we're talking about, because I'm still a little unsure.

The upper and lower buffer boards are attached to the Y-SUS by rigid header pin connectors. To disconnect the buffers from the Y-SUS, the Y-SUS board will have to be un-screwed and then pulled apart from the buffer boards.

Also, I tried to disconnect the orange PDP ribbons from the buffer boards, but can't figure out how they come out. There is a black flip up lever on the opposite side of the white housing from where the ribbon goes in. The white housing seems fixed to the board. The ribbon is locked in there somehow, and you can't get a good grip on it. Is there a special tool or trick to pulling the ribbon out?

Thanks for the help.

UPDATE:
I just found a blown surface mount cap, C873 on the upper Y buffer board. It goes between the ground screw pad and the big pad next to the ribbon connector that connects the upper and lower boards. So, now, why did it blow? Fault of the Y-SUS board? Do I just replace all 3 Y boards at once?

I have the same TV with the same symptoms, however, the surface mount cap that is blown is on the lower buffer board, C975. Did you ever find the value of these caps or a service manual? Did you try your replacement buffer with the old y-sus?

What I'm getting at is can I replace the buffer and skip the y-sus

[uncaged]

Re: LG 60PB6650 plasma flashes gray, then nothing

No, never found the proper service manual for this model, and don't know the value of those little caps.

I never tried the old Y-SUS with the new buffer because when I took it off it had a big discolored, overheated looking area on the back of the board under where the big cylindrical coil is mounted and under the little black coils next to it. It wasn't worth risking using it with the new buffer board.

Also, as a summary update, this was the repair sequence so far:

The power supply board would go straight to "on" mode when AC cord plugged in, and replacing the main board (with the AV jacks on it) fixed that situation.

Now, the power functions seemed correct, but still no picture. Replaced the Y-SUS and upper buffer board, and now the TV functions, but there are 2 thin horizontal lines across the top of the screen.

I've ordered another upper buffer, but I kind of suspect the ribbon cable connection might not be made correctly. Those ribbons from the PDP into the upper buffer are hard to insert in the connectors and getting them perfectly seated is completely shady.

[notsogentle]

Re: LG 60PB6650 plasma flashes gray, then nothing

No, never found the proper service manual for this model, and don't know the value of those little caps.

I never tried the old Y-SUS with the new buffer because when I took it off it had a big discolored, overheated looking area on the back of the board under where the big cylindrical coil is mounted and under the little black coils next to it. It wasn't worth risking using it with the new buffer board.

Also, as a summary update, this was the repair sequence so far:

The power supply board would go straight to "on" mode when AC cord plugged in, and replacing the main board (with the AV jacks on it) fixed that situation.

Now, the power functions seemed correct, but still no picture. Replaced the Y-SUS and upper buffer board, and now the TV functions, but there are 2 thin horizontal lines across the top of the screen.

I've ordered another upper buffer, but I kind of suspect the ribbon cable connection might not be made correctly. Those ribbons from the PDP into the upper buffer are hard to insert in the connectors and getting them perfectly seated is completely shady.

alright, thanks for the update, i've had a look at my y-sus and it seems pretty good. Just waiting on the buffer boards and I'll post back as well

[Hamie]

Re: LG 60PB6650 plasma flashes gray, then nothing

The caps are 2nf

[uncaged]

Re: LG 60PB6650 plasma flashes gray, then nothing

Hamie, thanks for following up with the cap value! I'll use that for my original board.

Final summary for me is that the TV works 100% again. I had purchased the Y-SUS and upper buffer boards from hotpriceparts. With the horizontal line issue, they were saying that it wasn't their upper buffer board, that it was my PDP. In the mean time I bought another upper buffer from shop jimmy. Installed that and the lines are gone and the picture is fine again. HPP did eventually issue a refund for the bad board.

Thanks for all the help everyone!

[Jsikora]

Re: LG 60PB6650 plasma flashes gray, then nothing

Hamie, I also have the same problem with c873 bad. Can you tell me the voltage of this 2nf cap and or where I may be able to find these. Thanks.

[Jsikora]

Re: LG 60PB6650 plasma flashes gray, then nothing

Does anybody have the info of chip c873 on board EBR77186101

[tom66]

Re: LG 60PB6650 plasma flashes gray, then nothing

I do not know the exact rating, but you should be safe with 1000V or 1250V (1kV or 1.25kV).

[Jsikora]

Re: LG 60PB6650 plasma flashes gray, then nothing

And this is a 2nf smd capacitor?
Digikey only has a 50 or 100V any idea where I could find these. Thanks for your help.

[tom66]

Re: LG 60PB6650 plasma flashes gray, then nothing

Show us a picture of it?
If it's surface mount - on the bottom, "green side" of the PCB, get us a measurement as best you can as well, in mm if possible.

[Jsikora]

Re: LG 60PB6650 plasma flashes gray, then nothing

Here are pics. C878,77,76 all appear to be the same or close to them same physical dimensions and I would say maybe 4mm long? My eyes are not the greatest. Thanks for the help.